The present invention is directed to a regenerative pump, sometimes referred to as a peripheral pump, specifically designed for the automotive industry, for use in conjunction with automotive engines to function as an inlet air pressure booster, mainly when the engine delivers power in excess of what is required for cruise.
This pump will meet the needs of various acceleration and engine power at a given shaft speed of the pump, by changing the specific output of said pump. This objective and the means to achieve it will be clarified.
In another application that involves pumping liquid, a pump provided for the purpose of supplying lubrication oil to bearings of an automotive engine or an automotive transmission, may be advantageously created along the lines about to be described. With such a pump the increase in pressure normally experienced at higher engine speeds, may be avoided by an adjustment to the inlet porting or the size of the chamber. As a result, less driving power will be needed to drive the pump at high engine speeds.
The two uses mentioned above may be of particular interest, but there are other needs that may be met and satisfied in industrial and chemical fields.
Commonly, these regenerative pumps are provided with an impeller having straight radial blades that terminate at their inner extremity into an arcuate wall that subtends generally a quadrant, and forms an inner portion of the fluid circulating chamber. Examples of these pumps may be obtained from U.S. Pat. Nos. 5,302,081, 5,205,707 and 5,163,810. There is also a related pump design that features what may be described as xe2x80x98salientxe2x80x99 vanes that project from a generally radial or wholly radial surface of the impeller. This is a feature that is opposed to the xe2x80x98set inxe2x80x99, or machined vanes of the usual design, that terminate at their inner extremity into an arcuate wall, that forms one of the inner quadrants of revolution, of the fluid chamber. Details of this version may be obtained from an ASME paper 76-WA/PID-22, authored by Sixsmith and Altman. The Sixsmith pump in utilizing the so called xe2x80x98salientxe2x80x99 vanes allows succeeding entry of circulating fluid to do so with little loss through a reasonable match of fluid and vane angles. This is a feature that cannot be accomplished with the aforementioned xe2x80x98set inxe2x80x99 vanes, and it explains why the older traditional designs have efficiency limited to 45% compared to a xe2x80x98salientxe2x80x99 vaned pumps efficiency of 58% or more. The superior vane entry conditions also confers a greater specific pressure and flow
It should be explained that both of these pumps are provided with a surrounding casing that forms a closed, so called xe2x80x98toroidalxe2x80x99 chamber, that permits repeated entry of air or other fluid so that successive added pressure may be accumulated at each completed convolution. The chamber may be generally circular in a cross section cut along the axis of rotation, or it is sometimes has a radial cut section that is rectangular with rounded corners. This chamber traverses most of the circumference of the outer reaches of the pump but is interrupted by an inlet port and an outlet port, which are separated by a small region of close fitting section that envelops the vanes of the impeller, so termed the xe2x80x98stripperxe2x80x99 section. Another aspect of these pumps is that they may be single sided or double sided. It is here noted that the improvements about to be described pertaining to the pumps as just mentioned, apply to both single and double sided versions.
The present invention applies to all the above described pumps and seeks to confer similar benefits to all of them.
A close examination of the theoretical operation of this general type of pump has revealed that a relationship exists linking the number of convolutions of the fluid; the mean spiral flow path allowed by the sectional size of the toric chamber; the angle of fluid entering and leaving the vanes; and the circumferential span of the inlet and outlet porting.
Observation of the performance of pumps made in the past have shown that of the variables immediately listed above, the circumferential span of the inlet porting has a major influence on performance. Past observation has revealed that when the inlet passage is widened, the fluid flow correspondingly increases. The increase in flow is caused by an increase in the width of the convoluting fluid mass. It will also be understood that the number of convolutions will be correspondingly reduced. This will cause a decrease in the maximum pressure generated by the pump. It is found that the increase in flow will correspond broadly and directly to the width of the inlet port. The maximum pressure will fall in more or less the same proportion.
Now consider that the pump is working against a pneumatic or hydraulic load such that the operation point on the pumps pressure/flow characteristic occurs at the mid point at half the maximum pressure and half the maximum flow. (It will be appreciated that the broad operating characteristic of all these pumps follow a pattern defined by a line extending from a point of maximum pressure at zero flow to a point of zero pressure gain at maximum flow). In the case just defined, any change to inlet port size will not change the operation of the pump as the point of operation is in a neutral position. However, should the hydraulic or pneumatic load be chosen to occur at a flow exceeding the mid, or neutral region, just mentioned, the counter clockwise swing of the characteristic about the aforementioned neutral region, (as the inlet port increases in span), will cause a rise in pressure to occur.
It is an object of the present invention to provide pressure increases on demand when said pump rotates at any given speed. According to a first aspect of the present invention, in a regenerative pump, whether it may be provided with simple set-in vanes, or salient vanes protruding from an otherwise smooth surface of its impeller rotor, means are provided to permit variation of the circumference span of the inlet porting, such that when the operating point of the pump is chosen to be at a point beyond the mid point flow range, an increase in pressure will occur as the span of the inlet passage increases.
In a second aspect of the present invention, a pump as just described will be made to operate such that the operating point occurs at a flow below the so-called neutral or mid-region flow. In this aspect of the present invention, the same or similar means for varying the span of the inlet passage/s are provided, but conversely to the first aspect just described, the pressure increase will take place as the circumference span of the inlet passage is reduced.
According to a third aspect of the present invention, means are provided whereby the width of the chamber may he varied by providing an axially slideably outer wall or walls according to whether the pump is single or double sided. In a fourth aspect of the present invention, irrespective of where the operating point is chosen, means are provided whereby the inlet fluid passage may be varied such that the desired pressure may be generated as previously explained.
In all aspects that have just been described, means of pressure/flow variation may be applied to single or double chambers. In the case of double chambers, flow varying means may either be confined to one chamber or applied to both.